This invention relates to vehicle wheels that have inflatable tyres and in particular to devices that are fitted on the rim of a wheel inside the tyre to enable the wheel to run with a deflated tyre. Such devices will hereinafter be called “run-flat devices”. The present invention is concerned with clamping devices for clamping together segments of a segmented ring run-flat device.
With conventional wheels that are not fitted with run-flat devices, when the tyre becomes deflated the tyre becomes damaged and can become shredded or thrown off the metal wheel rim. This can cause the vehicle to which the wheel is fitted to loose control, thus endangering other road users. At best, the vehicle can be stopped and the wheel replaced with a spare wheel, or the puncture repaired, or a new tyre fitted to the existing wheel. For commercial vehicles, such as lorries, this is very time consuming and costly because of the need to acquire specialist breakdown or repair services to get the vehicle back on the move again.
With lorries, military vehicles, carriers, such as bullion carriers, security vehicles, or other vehicles where a puncture of a tyre effectively halts the vehicle, and exposes the vehicle to danger from an external threat, there is a need to be able to continue with the vehicle journey irrespective of the deflated tyre.
When a tyre deflates partially or completely, the effective diameter of the wheel with the deflated tyre becomes relatively smaller compared with the wheels with inflated tyres. Therefore, the frictional engagement of the deflated tyre on the road causes the peripheral speed of the deflated tyre to increase to match the peripheral speed of the inflated tyres.
Simultaneously, any differential gearbox in the transmission drive path to a wheel with a deflated tyre will divert torque away from the driven wheels that have inflated tyres to the wheel with the deflated tyre. This in turn causes rotation of the deflated tyre relative to the metal wheel, particularly where the metal wheel is a driven wheel.